The House Sparrow, thanks to deliberate and not so deliberate introductions, is the most widely distributed bird in the world. In Britain, we have a population of more than five million pairs, making them one of our commonest species; they are familiar to us all, whether we live in the heart of the city or deep in the countryside. Yet, if you look at the data, these are birds that are in big trouble, especially in England. So what is going on with the House Sparrow?

The sad truth is that this common bird has experienced a drastic decline in numbers since the 1970s, it may still be a common bird, and a population of more than five million pairs sounds impressively large, but when you compare it to the 12 million pairs that we had in Britain in the 1970s you start to see there is a problem. A big problem.

If the humble, ubiquitous Sparrow continues to decline at that rate it will be extinct in Britain within my lifetime. Surely, as I sit here writing this, listening to the House Sparrows in my garden squabbling over the food, that can’t happen, can it? The House Sparrow’s native range is large, extending throughout Europe and into Russia and Asia, down into the Middle East and the Arabian Peninsula, as well as encompassing India and Bangladesh. Thanks to deliberate introductions, the bird has spread right across the globe.

In America, it was first introduced from England into New York City to control the caterpillars of the Linden Moth which were ravaging the many Lime trees planted within the city.

This wasn’t the best of plans, not least because, other than when they are feeding their chicks, the diet of the House Sparrow is very much seed-based (although they have now readily adapted to exploit our untidy ways when it comes to rubbish and food) and not caterpillar-based!

Pic: Glenn Bartley/Alamy

House Sparrows have proven themselves to be prodigiously invasive. It was first introduced into New York in 1863 and is now the most abundant bird in North America, being found everywhere from the Arctic-hugging Northwestern Territories of Canada, down to the tropics of Panama. Just seven years after that North American introduction, House Sparrows were introduced to South America, being released in Buenos Aires, Argentina in 1870.

Nowadays it can be found right at the southern tip of the continent, in Tierra del Fuego, and all the way up the Andean coast almost meeting up with the North American birds in Panama.

Other introductions in Tanzania in 1900 have led to the bird being found across a large part of southern Africa and, following an introduction in 1863, most of eastern Australia is now home to these small birds. Once they have been introduced, House Sparrows are able to increase their range at an astonishing rate, sometimes expanding it by 140 miles a year!

The House Sparrow, therefore, is a bird that can do extremely well in a variety of habitats. It is able to expand rapidly and is able to live alongside man in country and urban situations throughout the world. That makes the fact that the bird has had such a sharp decline in Britain extremely worrying; if the House Sparrow is struggling in Britain, what chance have other birds got? The House Sparrow is a brilliant little bird, but because it is so ubiquitous, so well known, it isn’t always appreciated, even by us birdwatchers, who can often be very dismissive of them when out birding.

The fact is they are a very interesting species and because they are still relatively common and often live in close proximity to us they are an excellent species to study. Being able to watch a bird closely allows us to identify many aspects of bird behaviour. What better bird to practise your birdwatching skills on than the House Sparrow?

Studies have shown that this small bird is actually long lived for its size, with one bird in Denmark living for at least 19 years; the typical lifespan is between three and four years.

This may seem low, but similar sized birds such as Dunnock and Robins have a typical lifespan of two years. House Sparrows form strong pair bonds, and are essentially monogamous. However, as is typical of many so called monogamous bird species, about 15% of the chicks that fledge are the offspring of a different male from the male bird of the pair.

Not all the birds in a breeding population form pairs, though, and these unpaired birds often act as helpers to the paired ones, helping them raise their broods. This help is probably very important, as a breeding pair will often have three broods (sometimes four) of four-five chicks per brood, and without it, it is questionable whether the House Sparrow could be such a prodigious breeder.

As already mentioned, House Sparrows have a diet of mainly seeds, but the young in the nest have a diet of insects. They cannot survive on dry seeds, and as they have no access to water while in the nest, they get their moisture from juicy insects, which are also packed with vital protein.

Many of our insect-feeding bird species have shown population declines as the sparrow over the same period and there is no doubt that our abundance of insects in Britain has been severely diminished in recent years.

Pic: Tim Gainey/Alamy

As a child, I remember what we used to call ‘Insect Rain’ – the splatter of insects hitting the car windscreen as you drove along on summer evenings – making a real mess of the windscreen and front of the car. This still happens in many parts of Europe, but you may have noticed that it hardly ever happens in England now. The intensification of agriculture and the subsequent development of newer and more lethal insecticides are blamed.

Fewer insects in the environment means less birds that depend on them. Changing agricultural practices are more than likely the cause of the decline of Sparrows in the countryside, but House Sparrows are also declining in our cities and urban environments, too. In fact, the decline in these areas is more rapid than the decline in the countryside, at the moment no one is quite sure what is causing this decline, but it is extremely worrying.

They might not be yellow and they might not sing a pretty tune, but if such a successful bird is declining in our urban environments then perhaps they are fulfilling the role of the canary in the coal mine, warning us of impending danger.

House Sparrows may be very common, we may see them regularly, but we most definitely cannot take them for granted. They are in trouble, and that should concern us all.